Protective device



B. L. STEMMONS.

PROTECTIVE DEVICE.

APPLICATION FILED MAY 20. 1918. RENEWED JULY 20,1921.

Patenteol Nov. 192;

limltllll Inventor" Bevefln g .L, .Stemm'ons,

His Attornag.

UNITED STATES PATENT OFFICE.

BEVERLY L. STEMMONS, 01 CHARLOTTE. NORTH CAROLINA, ASSIGNOR ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

TO GENERAL PROTECTIVE DEVICE.

Specification of Letters Patent.

Patented Nov. 8, 1921.

Application filed Kay 20, 1918, Serial No. 235,447. Renewed July 20, 1921. Serial No. 486,186.

T 0 all whom it may concern:

Be it known that I, BEVERLY L. STEM- Moxs, a citizen of the United States, residing at Charlotte, in the county of Mecklenburg, State of North Carolina, have invented certain new and useful Improvements in Protective Devices, of which the following is a specification.

My invention relates to protective devices and more particularly to devices for the protection of electrical conductors from conditions of lightning disturbances, transients and other over-voltage phenomena. The object of my invention is to provide a device which is operative to relieve a conductor 'from excessive voltage conditions caused by transients, surges and similar phenomena, and more specifically to provide a spark gap device for use in outdoor service, which will discharge at its dry arcover voltage setting independent of weather conditions with a very short time delay between the application of arc-over voltage and the discharge across the device, and which is, in general, an improvement on similar devices of this nature heretofore known in the art.

It is known, as described in U. S. Letters Patent '#1,232,467, granted to Frank W- Peek, Jr., that a protective or spark gap device which comprises two cooperating electrodes having their proximal surfaces in the form of surfaces of revolution, such as two spheres, and separated by a certain distance relative to the radius of the spheres, forms a spark gap having a substantially uniform dielectric field. When arc-over voltage occurs across such a gap, there is a minimum time delay between the occurrence of arc-over voltage and the rupture of the dielectric or the discharge across the gap, that is, there is no formation of brush discharge or corona prior to the discharge of the gap to introduce a time delay. A sphere gap so proportioned is very fast and serves quickly to relieve the conductor to be protected from all excessive voltage conditions and particularly surges of steep wave front. An arrester comprising a gap 'is better adapted for outdoor service if the gap is protected from the weather, as weather con ditions, such as rain, snow andice collects on the electrodes and serve to lower the voltage at which an arc-over will occur as the arc-over voltage of a gap under Wet conditions, or the wet arc-over voltage is less than the arc-over under dry conditions or the dry arc-over voltage.

According to my invention, I utilize the speed of the properly proportioned sphere gap, together with means whereby an arrester comprising such a gap may be operated outdoors and controlled by its dry arc-over voltage setting and hence at maximum efliciency. I obtain the dry arc-over setting by providing an arrester having two spark gaps in series, one gap being protected from conditions of the weather and controlling the complete breakdown of the arrester and the other gap unprotected, in combination with a third gap of the horn type which is so related to the series gaps to take the are formed and cause its rapid extinguishment.

The novel features which I believe to be characteristic of my invention will be definitely indicated in the claims appended hereto, while the features of construction and method of operation will be understood by reference to the following description taken in connection with the accompanying drawing which shows, in perspective view, a protective device embodying the features of my invention.

As shown in the drawing, the protective device of my invention comprises two 00- operating electrode members 1 and 2, spaced apart and diverging from each other to form a horn gap 3. The electrode, or horn member 1, is mounted on an insulating member 4 and adjustably supported thereon by a clamping means or'member 5. The horn member 1 is adapted to be connected to one terminal of the arrester, and preferably to the conductor to be protected, when the device is connected between a conductor and ground, by means of a suitable connection such as terminal member 6. The cooperating electrode, or horn member 2, rests upon and in engagement with a protecting hood or umbrella-shaped member 7 preferably of metal. The umbrella-shaped electrode, or

member 7, is insulated and, for this purpose,

electrode 7 and protected thereby, is an elecweather and which I desire to designate the main gap The sphere electrode 10' is adapted to be connected tothe other ter- 10- minal of the arrester and preferably to ground when the arrester is connected between line and ground. As one convenient means of mounting the spherical electrode 10, Ihave shown the insulator 8, with the umbrella electrode 7, sn ported by a conducting member 12 whic is preferably in the form of a metal strip of sufiicient thickness to enable the insulator 8 with its umbrella member to be supported rigidly. This conducting member 12 is adapted to be connected to one terminal of the arrester and I adjustably mount upon this conducting member 8 and in conductive relation therewith, the spherical electrode 10.

Adjustably mounted upon the horn electrode 1 is an electrode member 13 consisting of a surface of revolution and preferably a sphere which, in the form shown, is slidable on the horn member 1 and adapted to cooperate with the outer surface of the umbrella electrode 7 to form a spark gap 14 which is in series with the main gap 11 but unprotected from weather conditions. I prefer to designate the spark gap 14, the auxiliary spark gap. It will be observed that the space between the. two spherical electrodes 10 and 13 is divided into two gaps 11 and 14 in series by the common electrode or umbrella 7, one gap 14 being unprotected electrodes 1 and-2 take the arc and it rises and the other gap 14 being protected by the umbrella 7. When a complete discharge of the gaps 11 and 14 takes place, the horn quickly on the horns and is extinguished.

The horn gap 3, main gap 11, and auxiliary gap 14 may have various relations, but for most eflicient results I prefer to ad-' just auxiliary gap 14 for a dry arc-over voltage of approximately 75% of the are over voltage of the main gap 11=and horn gap 3 for a normal frequency arc-over voltage 10% higher than that of gap 14.-

The dry arc-over voltage setting of'main gap 11 determines the complete gap sparkover. With this arrangement static sparkover will not occur under normal dry operating conditions, but if the potential is increased gap 14 will first arc-over and if the potential .is still further increased complete spark-over of the gaps 11 and 14 will occur. What I claim as new and desire to secure by Letters Patent of the United States,is 1. In a protective device, two cooperating electrodes having their proximal surfaces in the form of surfaces of revolution and gap '11 which is protected from the spaced apart to form aspark gap, of an umbrella member forming a common electrode between said cooperating electrodes spherical and spaced apart to form a spark gap, a third electrode member coacting with 1 said cooperating electrodes to form two spark gaps in series and shaped to partially inclose one of said electrodes to protect one of said spark gaps from the weather- 3. In'a protective device, the combination of an umbrella member, of an electrode beneath said umbrella and an electrode outside said umbrella cooperating therewith to form two spark gaps in series, one of said gaps being protected from the, weather and the other gap being unprotected.

4. In a protective device, an insulated metallic umbrella member, an electrode beneath said umbrella and spaced away from the same to provide a spark gap having an arc-over voltage independent of weather conditions, a cooperating electrode outside said umbrella and spaced away from the same to provide a second spark gap. 4

5. In'a protective device, the combination with two cooperating electrodes separated to form a spark gap, of a conducting hood member extending into said gapand partially inclosing one of said electrodes to provide a main spark gap between said hood member and the inclosed electrode and an auxiliary spark gap between said hood member and the other of said electrodes.

6. In a protective device, the combination with the cooperating electrodes having their proximal surfaces spherical and spaced apart to form a spark gap, a third electrode member extending between said cooperating electrodes andshaped to partially inclose one of said electrodes, and means for extinguishing arcs formed between said electrodes. 7. In a protective device, the combination with an umbrella member, of an electrode beneath said umbrella and an electrode outside said umbrella cooperating therewith to form two spark gaps in series, and 006perating horn gap members inconductive relation with'said outside electrode and said umbrella.

8. A protective device comprising an umbrella electrode, a cooperatingelectrode beneath said umbrella and spaced away from the same to provide a spark ap, an arcing horn carried by said umbrel a electrode, a cooperating arcing horn, and. a third electrode carried by said cooperating horn and BEVERLY L. STEMMONS. 

